TENSIOMETER BASED AUTOMATED IRRIGATION FOR TOMATO UNDER PLASTICULTURE - Management, Performance, and Applications of Micro Irrigation Systems - page 208

16,750 kg·ha -1 in 2009 and 9750 kg·ha -1 in 2010; a reduction of approximately 41%.
However, yields of large and extra large fruit were reduced by 67% and 77%, respec-
tively, in 2010. This reduction in yield of large and extra large fruit was refl ected in
average fruit weight, which was reduced from an average of 287 g/fruit in 2009 to
105 g/fruit in 2010. Air temperatures during the summer of 2010 were supra optimal
for fi eld tomato production in Kentucky [16]. The higher than normal temperatures
in July and Aug. 2010 resulted in yield losses for many fruiting vegetables in Ken-
tucky [28, 33].
In both years of this trial the −45/-40 kPa treatment used the least water. The
most typical irrigation practice for fresh market tomato growers in Kentucky
would be refl ected in the −30/-10 and −40/-10 kPa treatments where plants may
be watered for three or four hours, once or twice per week. Trials conducted with
sandy soils reported similar water savings through pulsed irrigations, without sig-
nifi cant differences in yield compared to typical grower practices [20, 42]. This
suggests that irrigation practices may be altered in Kentucky to achieve additional
water savings.
Predawn and midday plant Ψ L and leaf RWC were analyzed to determine if physi-
ologic stresses were imposed. Predawn and midday Ψ L were not affected by irrigation
in 2009 and 2010 (Fig. 2A-D). In both years, midday Ψ L was signifi cantly greater than
predawn Ψ L . The increase in Ψ L from predawn to midday varied according to sampling
date. On 6 Aug. 2009 Ψ L increased from 0.6 MPa predawn to 7.7 MPa midday, but on
1 Sept. 2010 Ψ L increased from 4.2 to 7.6 MPa at predawn and midday, respectively.
In 2009 a decrease in predawn Ψ L was observed on 6 and 18 Aug. (Fig. 2C), which
occurred after a rain event (Figs. 1A to 1E). In 2010 predawn Ψ L increased signifi -
cantly on 28 July and 11 Aug. (Fig. 2D), which did not correspond with a particular
rain event, but did correspond with a period of daily high air temperatures greater than
90°F. Another study [21] reported similar fl uctuations throughout the growing season
when measuring Ψ L bell pepper.
Predawn water potential was signifi cantly greater in 2010 than in 2009. Average
predawn Ψ L for the 2010season was 4.2 MPa compared to 2.2 MPa in 2009 (Figs. 2C
and 2D). This may be due to the higher temperatures observed in the 2010 growing
season. Positive correlations between Ψ L and air temperature were reported [7, 26].
Although environment affected Ψ L in 2009 and 2010, irrigation regime was not shown
to signifi cantly affect Ψ L .